<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body>

<script type="text/javascript">
function fnArr(arr){
	var newArr = [];

	arr.forEach((item,index)=>{
		newArr.push( Math.max(...item)  )
	})

	return newArr;
}
console.log(fnArr([
	[4,5,1,3],
	[13,27,18,26],
	[32,35,37,39],
	[1000,1001,857,1]
]));
</script>

</body>
</html>